How to UV unwrap holodeck model
Overview:



It's fairly simple setup but there is a little thing you should be aware of at the start. Proportions of your model should be even or squared (I'm not sure how to put it). In this example it's a box 1x2x0.8m. When you put something like 1.12x2.43x0.63m pattern will not create perfect grid. Also remember to Apply Scale of your mesh.

Mesh and Seams:




  First of all it's a bad topology (ngons) but I've leaved it as is for
  simplicity sake.



For beveled corners you should use even number of Faces to have an Edge in the center of them.
Mark Seams in a way to cut off walls, floor and ceiling.


UV Map:




Select all and Unwrap the mesh (U > Unwrap).
Go to Image Editor, select UV Islands one by one (L while hovering over an island) and Snap them to the cursor by Shift+S > Selected to Cursor (Offset).




You can rotate islands that are vertically placed if you want but it's not necessary.

Lining up grid:

There are two methods to line up grid and resize it (I don't know how to do it perfectly).


You can just select all UV Islands and Scale them up/down.
You can use Mapping node to set the grid size. I've used this method.




Blend file: